This invention relates in general to the monitoring of tension in a moving web and in particular to an improved system for coupling forces generated in response to that tension to a sensor.
In various industries, the monitoring of tension in a web which may be moving at a high speed is essential to avoid damage to the web or to maintain proper manufacturing controls. For example, in the manufacture of paper, endless fabric webs are frequently used; and if tension is insufficient, the fabric tends to wrinkle, forming irregularities in the material being carried by the web. Conversely, if tension becomes too great, the web may be destroyed. In many other applications, such as printing presses, and textile manufacturing, it is necessary to continuously observe and maintain tension within suitable limits.
Numerous systems have been devised for such tension monitoring. One such system is exemplified in U.S. Pat. No. 3,260,106, in which the web is passed over a guide roll and exerts displacing forces upon that guide roll. The guide roll is mounted for rotation upon a shaft or a pair of stub shafts and the forces exerted by the tensioned web upon the guide roll causes deflection of the supporting shaft or shafts which is sensed by a strain gauge or gauges.
In the device of that patent, a diaphragm is employed to couple the guide roll shaft or shafts through the sensor to fixed frame members which support the entire apparatus. The diaphragm permits minor amounts of shaft misalignment, as well as expansion of components to occur without seriously affecting the accuracy of the measurements. However, the diaphragm is limited in the amount of tolerance which it has for such variables. Moreover, the life of the diaphragm is somewhat limited because flexing leads to fatigue of the material and rupture of the diaphragm is a relatively short period of time. It is therefore the primary object of the present invention to improve the measurement and monitoring of the web tension by incorporating a superior coupling mechanism between the fixed frame members and the guide roll through a strain gauge system.